Cardiac cycle, ECGs & Murmurs BECKY & SHEF

ECGs

What does an ECG show?  Normal electrical activity of the heart  Abnormal electrical activity of the heart  Abnormal Heart Rhythms  Myocardial Infarction  Enlarged Heart

ECG Leads  Limb leads  Coronal plane  Placement:  Right arm  Left arm  Left leg  Right leg (Neutral electrode – serves as reference electrode)  Chest leads  Transverse/Horizontal place  Placement:  (See next)

Chest leads positioning  V 1 - Right 4 th ICS, just lateral to sternum  V 2 - Left 4 th ICS, just lateral to sternum  V 3 - Between electrodes V 2 & V 4  V 4 – 5 th Left ICS, MCL  V 5 - Between electrodes V 4 & V 6  V 6 – 5 th Left ICS, MAL

Summary of limb lead placement ElectrodeElectrode placement RA Right arm, avoiding thick muscle. LA Left arm, avoiding thick muscle. RL Right leg, lateral calf muscle. LL Left leg, lateral calf muscle. V1V1 Fourth right intercostal space, just lateral to the sternum V2V2 Fourth left intercostal space, just lateral to the sternum V3V3 Between electrodes V 2 and V 4. V4V4 Fifth left intercostal space, mid-clavicular line. V5V5 Between electrodes V 4 and V 6. V6V6 Fifth left intercostal space, midaxillary line.

Lead view of the heart

12-lead ECG

Analysing ECGs

ECGs Atrial depolarisation Ventricular depolarisation Ventricular repolarisation

STEMI vs Non-STEMI (NSTEMI) NSTEMI account for about 30% and STEMI about 70% of all MI’s. NSTEMI – Occlusion of a minor coronary artery or partial occlusion of a major coronary artery STEMI – Complete occlusion of a major coronary artery. Transmural damage. Symptoms – Chest pain, vomiting, sweating, difficulty breathing SAME IN BOTH

Theory! Injured cells are leaky, will repolarise quicker than the healthy cells. Injured area repolarises quicker, causes a flow of electrical signal towards the injured area – detectable on an ECG Absence of electrical activity. A myocardial infarction can be thought of as an electrical 'hole' as scar tissue is electrically dead.

Hyperkalaemia  High/tented T wave  Prolonged PR interval  Widened QRS complex  P waves low or absent  Depressed ST segment  Atrial standstill  Intraventricular block  Bradycardia  Ventricular fibrillation  Asystole

Hypokalaemia  Low T wave  High U wave  Low ST segment

Approach to treatment of hyperkalaemia & hypokalaemia  Hyperkalaemia (≥7.0 mmol/L, or any increase associated with ECG changes)  Immediate  Stop any K+ supplements or K+ conserving drugs  Administer calcium gluconate intravenously (for cardiac protection)  Short term  Insulin/dextrose to encourage K+ uptake into cells – MONITOR GLUCOSE  Salbutamol (Beta2-agonist)  Long term  Loop diuretics  Calcium resonium  Dialysis  Hypokalaemia (<3.5 mmol/l, but may not have symptoms until <2.5 mmol/l)  Change diet (Bananas very K+ rich)  Change/stop diuretic  Can infuse with K+ if needed

Cardiac Cycle

A (See notes below for full summary) B C D

Heart Sounds & Murmurs

Heart Sounds  I + II + 0  S1 (‘Lub’) + S2 (‘Dub’) + No added heart sounds  S1 – Closure of mitral & tricuspid valve  S2 – Closure of aortic and pulmonary valves  S3  Oscillation of blood back and forth between ventricle walls  Occurs following S2  Suggestive of congestive heart failure  S4  Atria contracting forcefully in an effort to overcome an abnormally stiff or hypertrophic ventricle  Occurs just before S1 (Mitral valve closure)  Suggestive of a failing or hypertrophic ventricle

Heart valve auscultation points

What is a murmur?  Turbulent flow of blood strong enough to produce audible noise

AS MR. ARMS SAYS… ASMR|ARMS SYSTOLE DIASTOLE  AS – ejection systolic (Mid-systolic)  MR – pansystolic  AR – early diastolic  MS – mid-diastolic